Biomedical subjects

H Asou

Publications and source records attributed to H Asou.

At least 19 recordsLinked to original sources

PubMed1995

Decrease of NCAM expression and astrocyte-neurone interaction in long-term cultured astrocytes.

In order to assess the characteristics of the older astrocyte, we obtained long-term cultured rat astrocytes (20 months) and examined the features of protein expression in relation to neuronal interaction. In short-term cultured astrocytes, NCAM expressed strongly in contrast to weak expression of laminin by both immunocytochemical and ELISA assay. On the contrary, in long-term cultured astrocytes, a marked decrease of NCAM expression was observed along with increased laminin expression compared with short-term cultured astrocytes. The long-term cultured astrocytes remained positive to anti-GFAP antibody and showed a much lower ability to interact with neurones than the short-term cultured astrocytes. NCAM may be one of the responsible molecules related to the astrocyte-neurone interaction in the developing and ageing nervous system.

Animals↗

PubMed1995

Grafts of genetically modified fibroblasts expressing neural cell adhesion molecule L1 into transected spinal cord of adult rats.

L1, a neural cell adhesion molecule, is known to promote neurite elongation via a homophilic interaction in vitro. In the present study, fibroblast L cells that were genetically modified to express the L1 molecule were grafted to a lesion of rat spinal cord immediately after hemisection. Grafts drastically promoted regeneration of the axons in the injured spinal cord 2 weeks after grafting. A number of regenerating axons penetrated the glial scar along the host-graft interface, and elongated into the graft. These results suggest that grafts of genetically modified cells expressing L1 can provide an environment suitable for regeneration of the axons in the injured spinal cord.

Animals↗

PubMed1995

CNS myelinogenesis in vitro: time course and pattern of rat oligodendrocyte development.

Oligodendrocyte precursor cells that develop into myelin-forming cells of the central nervous system (CNS) were cultured from newborn rat brain to study how they proliferate and differentiate in normal conditioning medium, and their cell development was characterized by scanning electron microscopy (SEM) observation and immunocytochemical studies. We have identified A2B5-negative pre-O2A progenitor cells (so-called "type-1" oligodendrocytes) in the secondary cultures on the astrocyte feeder layer. These cells are very small (diameter: 3.5 microns), round, and glossy, and develop into the process-bearing O2A progenitor cells (called "type-2" oligodendrocytes), which also express myelin basic protein (MBP) both in the cell body and in their cell processes. Finally, they develop into mature oligodendrocytes (called "type-3" oligodendrocytes). After MBP expression is elicited in these cells and MBP accumulates in the cell process in the area in contact with the axon, these cells are capable of forming the myelin sheath. Therefore, we examined the mechanism of myelin-sheath formation of "type-3" oligodendrocytes using video time-lapse movies, and demonstrated that these cells initially sent out processes to search for axons several times before the onset of myelination. Then thick filopodia extended towards the axon, and at the same time, the axonal part of neuron moved forward. Finally the ruffling lamellipodial parts wrapped up the axon similarly to a transverse wave with the secured thick filopodial process on the axon acting as scaffolding. These results suggest that our experimental systems are useful in studying normal oligodendrocyte development and their cellular biochemistry, as well as investigating the mechanism of myelin formation by oligodendrocytes.

Animals↗

PubMed1995

Identification of two transcripts of AML1/ETO-fused gene in t(8;21) leukemic cells and expression of wild-type ETO gene in hematopoietic cells.

The t(8;21) is a common chromosomal abnormality, preferentially associated with acute leukemia showing features of myeloid differentiation. Recently, two genes--AML1, which has a unique runt domain, and ETO (MTG8)--have been isolated from the chromosomal breakpoint. In this study, we isolated and identified two fused transcripts from a leukemic cell line carrying t(8;21). AML1 and ETO were fused at the same position in these transcripts. One of the transcripts codes a unique domain, including two zinc finger domains and three proline- and one leucine-rich region. The other transcript codes only for one proline- and leucine-rich region but lacks zinc finger domains. We demonstrated by polymerase chain reaction (PCR) analysis that 1) these two transcripts are consistently expressed in leukemic cells with t(8;21) obtained from patients and 2) expression of AML1 was not restricted to the particular stage of hematopoietic differentiation but was present in all hematopoietic cells investigated. We also provide evidence that two wild types of ETO transcripts containing the region of the ETO gene in fused transcripts are expressed in hematopoietic cells from different lineages. The widespread expression of AML1 and ETO in hematopoietic cells suggests a fundamental role of these proteins in hematopoiesis. Furthermore, the differences in the carboxy termini of ETO may modulate the activity of fused proteins resulting from the chromosomal translocation t(8;21).

Acute Disease↗

PubMed1995

Structure and function of peripheral nerve myelin proteins.

(1) Two glycoproteins, P0 and PASII, are widely distributed in the peripheral myelin, but not in the central myelin of mammals. P0-like protein is expressed in both peripheral and central myelins of some lower vertebrates, such as fish and tadpoles. A close relationship is suggested between P0 expression and neural regenerative activity. (2) PMP22 was reported to show high sequence homology, not only to PASII, but also to the growth arrest specific protein. Human PASII/PMP22 sequence was deduced and the locus of its gene, chromosome 17p12-p11.2, is similar to the region linked to Charcot-Marie-Tooth disease type 1A. (3) P0 expressed on cultured cells mediated strong homophilic cell adhesion and neurite outgrowth. Addition of the P0 glycopeptide inhibited cell adhesion markedly, indicating that the oligosaccharide with peptide is essential for P0 mediated cell adhesion. The active site for neurite outgrowth in P0 appears to be different from the adhesion site. (4) We determined the human chromosomal locus of the P0 gene, 1q22-q23, which corresponded to the locus of hereditary motor and sensory neuropathy, Charcot-Marie-Tooth disease type 1B. Point mutations in the extracellular domain of P0 are found in the patient's chromosome. (5) L1 is a large multifunctional adhesive glycoprotein of 200 kD. Rat and human L1 sequences confirmed a common structure for the mammalian nervous systems. An isoform of L1 (L1cs), lacking four amino acids, appears to localize in non-neuronal cells such as Schwann cells, while the complete L1 is exclusively found in neurons. L1cs in Schwann cells may be functionally different from L1 in neurons.

Amino Acid Sequence↗

PubMed1995

A specific chromosome abnormality of t(4;12)(q11-12;p13) in CD7+ acute leukaemia.

Three cases of acute leukaemia with t(4;12) (q11-12;p13) karyotypic abnormalities were analysed. They had the following common clinical and biological characteristics: (1) dysplasia of three haemopoietic lineages: (2) absent or low myeloperoxidase activity: and (3) retention of platelets in the peripheral blood and megakaryocytes in the bone marrow. There were increased numbers of basophils in the bone marrow and peripheral blood in two of the cases. In all, the blast cells displayed the unique immunophenotype CD7+CD13+CD34+HLA-DR+. The blasts analysed in one case expressed c-kit on the membrane surface. These findings suggest that the t(4;12) (q11-12;p13) abnormality is associated with a particular type of acute leukaemia, one in which the morphology and immunophenotype suggest that the translocation may have occurred at an early stage of haemopoiesis.

Acute Disease↗

PubMed1995

Emergence of karyotypically unrelated clone in remission of de novo acute myeloblastic leukaemias.

Serial cytogenetic analysis revealed karyotypically unrelated clones in four patients with acute myeloblastic leukaemia (AML) in remission. At diagnosis, three patients had t(8;21)(q22;q22) and one had an inv(16)(p13q22). After 18-22 months in remission, different clones emerged in each patient with myelodysplastic features of the bone marrow cells. The emergence of clones with abnormalities of chromosome 7 in remission seems to be an unfavourable factor for prognosis.

Antineoplastic Combined Chemotherapy Protocols↗

PubMed1995

Visualization of a single myelination process of an oligodendrocyte in culture by video microscopy.

We described the initial events in the interaction between an oligodendrocyte process and an axon in culture utilizing video time-lapse microscopy. Myelination of an axon by the lamellipodium of an oligodendrocyte was achieved in several steps of cellular process development and coordinated interaction between axon and oligodendrocyte. The initial stage of contact included the formation of a lamellipodium process at the end of an oligodendrocyte process. It appeared that this process contacted the axon several times and was then retracted, and that the filopodia and lamellipodium underwent morphological changes prior to the onset of the myelination. In the second stage, the lamellipodium appeared to thicken and anchor to the axon. Finally, when rippling of the lamellipodial ruffling occurred, the angle between the anchoring filopodium and the axon changed depending on the direction of lamellipodial movement, and the lamellipodium, which was folded in layers, wrapped around the axon like a transverse wave in one motion as observed on the video screen. Thereafter, the lamellipodium assumed a "bursting" form within minutes in real time. This is the first comprehensive overview of how an oligodendrocyte plasma membrane wraps around an axon to form myelin.

Animals↗

PubMed1995

Development of oligodendrocyte and myelination in the central nervous system.

We demonstrated the cell lineage of oligodendrocytes from the glial precursor cells to mature oligodendrocytes forming myelin sheath around the axon. There are several different stages of oligodendrocyte development in vito. So far there are no precise data about their morphological changes during oligodendrocyte development, but by the analysis using SEM and immunostaining, the characteristic morphological changes with serial expression of cell markers were observed in each developmental steps of oligodendrocyte. We have also clearly demonstrated how oligodendrocytes wrap around the axon by using video time-lapse movies. These results will be useful for understanding the exact cellular mechanism of myelination in the CNS.

Animals↗

PubMed1995

Independent clones of trisomy 12 and retinoblastoma gene deletion in Japanese B cell chronic lymphocytic leukemia, detected by fluorescence in situ hybridization.

Trisomy 12 and a deletion of chromosome 13 are the most common chromosome abnormalities in patients with B cell chronic lymphocytic leukemia (B-CLL). We determined the frequencies of these abnormalities in Japanese B-CLL patients by FISH in interphase nuclei. Specimens from 42 patients were analyzed using both DNA probes specific to the centromeric region of chromosome 12 and the retinoblastoma (RB) gene. Among 42 patients, eight had trisomy 12 and 12 had the RB gene deletion. We found aberrations of trisomy 12 and the RB gene deletion in a totally different group of patients. This suggested that the trisomy 12 and the RB gene deletion occur in different clones and the presence of which in the same patient may be rare. Furthermore, the frequency of trisomy 12 (19%) found in Japanese B-CLL was lower than that in Western countries (30-35%). On the contrary, the frequency of the RB gene deletion (28.6%) was almost the same as in European B-CLL (30-35%). These results will be helpful in understanding the leukemogenesis of B-CLL.

Adult↗

PubMed1994

Identification of a breakpoint cluster region 3' of the ribophorin I gene at 3q21 associated with the transcriptional activation of the EVI1 gene in acute myelogenous leukemias with inv(3)(q21q26).

Structural alterations occur in the long arm of chromosome 3 in approximately 2% of patients with acute myelogenous leukemia (AML) or myelodysplastic syndrome (MDS). The major alterations are inv(3)(q21q26) and t(3:3)(q21;q26) and are often classified as the 3q21q26 syndrome. We previously reported that the EVI1 gene is transcriptionally activated in AMLs with t(3;3)(q21;q26) and inv(3)(q21q26) and that the chromosomal breakpoints at 3q26 in the translocations were 5' of the EVI1 gene, whereas the breakpoints in the inversion cases were 3' of the gene. In these studies, four additional cases of AML with inv(3)(q21q26) are shown to express the EVI1 gene and to have breakpoints 3' of the gene. To characterize the 3q21 breakpoint region, cosmid and phage clones were isolated that cover approximately 100 kb. At 3q21, the breakpoints for both AMLs with t(3;3)(q21;q26) and inv(3)(q21q26) were found to cluster over a region of approximately 50 kb downstream of the Ribophorin I gene. The results indicate a common mechanism for the translocations and inversions and support the hypothesis that the transcriptional activation of the EVI1 gene is mediated by enhancer elements associated with the Ribophorin I gene.

Adult↗

PubMed1994

GFAP transfected cells produce laminin, leading to neurite outgrowth promotion.

Accumulating evidence indicates the importance of astrocytes in neuronal development and regeneration. While glial fibrillary acidic protein (GFAP) is believed to mediate the morphology of developing astrocytes, its precise function remains unknown. To analyse the function of GFAP in astrocytes, we established GFAP-expressing cell lines by transfection of mouse GFAP cDNA into mouse fibroblast L cells. Stable transfectants expressed GFAP uniformly in the cytoplasm with no phenotypic changes and exhibited extended processes rich in GFAP. GFAP-expressing cells significantly promoted the neurite outgrowth of rat cerebral cortex neurones in the co-culture system. Analysis of the products of GFAP-expressing cells revealed an increase in production of laminin, but not fibronectin. These results suggest that L cells expressing GFAP increase laminin production, leading to promotion of neurite outgrowth.

Animals↗

PubMed1994

Peripheral myelin P0 protein mediates neurite outgrowth of cortical neurons in vitro and axonal regeneration in vivo.

Peripheral myelin P0 protein is a homophilic adhesion molecule of immunoglobulin superfamily to compact myelin structure. In addition to its roles in formation and maintenance of myelin, P0 shows neurite-outgrowth promotion activity of dorsal root ganglions. In this paper, we examined biological activity of P0 in central nervous system (CNS). Neurite outgrowth of cortical neurons of rat embryo was markedly promoted in the co-culture on C6 transformants expressing P0 protein. The neurite outgrowth was not inhibited by the P0-glycopeptide but specifically inhibited by the anti-P0 monoclonal antibody recognizing the extracellular peptide of P0. In in vivo studies, we observed significant axonal regeneration into grafts only in animals implanted with P0-expressing transformants after spinal one-third transection. These results suggest that P0 protein has promoting activity on the neurite elongation in CNS as well as in peripheral nervous system.

Animals↗

PubMed1994

Production of hematopoietic stem cell-chemotactic factor by bone marrow stromal cells.

Chemotactic factors produced by stromal cells in the bone marrow are characterized. Two kinds of factors produced by stromal cell lines are identified using blind-well Boyden's Chambers; one is a neutrophil-chemotactic factor and the other a hematopoietic stem cell (HSC)-chemotactic factor. The latter attracts blastic cells in a low-density fraction, which are Thy1lo, wheat germ agglutinin (WGA)hi, H-2Khi, Ly-1-, Ly-2-, L3T4-, Ly5-, and slg-. The molecular weight of this HSC-chemotactic factor is estimated to be more than 200 kD. Putative cytokines and growth factors, such as granulocyte colony-stimulating factor (CSF), macrophage CSF, granulocyte-macrophage CSF, stem cell factor (SCF), interleukin (IL)-6, and IL-3, do not possess HSC-chemotactic activity. These findings strongly suggest that bone marrow stromal cells produce a new factor that attracts HSCs.

Animals↗

PubMed1994

How do oligodendrocytes ensheath and myelinate nerve fibers?

Oligodendrocyte precursor cells were cultured from newborn rat brain and studied their differentiation and proliferation. They have identified type-1, type-2, and type-3 oligodendrocytes based on the expression of characteristic marker molecules that frequently used to stage oligodendrocyte development. The type-3 oligodendrocytes were observed to send but tentative that locate axons prior to myelination. These processes terminate in lamellipodia, which eventually enwrap the axon and begin the myelination process with several steps. At the first stage, ruffling is immediately induced at the lamellipodia with filopodia made of oligodendrocyte processes, and the axon is contacted several times; then process retraction occurs to reform the filopodial and lamellipodial parts prior to the onset of the myelination. Second, after filopodial movements and lamellipodial ruffling occur again, their morphology is dramatically changed to become three thick filopodia that anchor to the axon. Finally, lamellipodial ruffling parts ripple, the angle between the position of the resting filopodium and the axon change, depending on the start of axonal movement, and the lamellipodia turn around the axon like a transverse wave with one stroke of the brush, as observed on the video screen, and their rolling membrane changes to the bursting form within minutes in real time.

Animals↗

PubMed1994

Expression and effects of hyaluronan and of the hyaluronan-binding protein hyaluronectin in newborn rat brain glial cell cultures.

Hyaluronan (HA) is a polymerized nonsulfated extracellular matrix glycosaminoglycan that may be involved in brain development. We have tested the expression of HA and the HA-binding protein hyaluronectin (HN) in glial cell cultures from newborn rat brain. HA was secreted into the culture medium by type 1 astrocytes in the first stages of the primary cultures. The secretion was high during cell proliferation, reached a maximum when they were confluent, and then decreased. HA was not secreted at a detectable level by total O-2A lineage cell-enriched cultures. HA labeled small O-2A progenitor cells (GFA-, A2B5+, HA+), small O-2A progenitorlike (GFA-, A2B5-, HA+) cells, and type 2 astrocytes (GFA+, A2B5+, HA+), but not mature oligodendrocytes (Galc+, HA-). In contrast to HA, hyaluronectin labeled oligodendrocyte membranes (i.e., more mature cells) from day 8. A2B5+ GFA- cells were found to be either HA+ or HN+ at days 7-9, suggesting intermediary stages. The addition of HA to primary cultures and to O-2A progenitor-enriched cultures decreased significantly the increase in the number of O-2A progenitors, of mature (Galc+) oligodendrocytes proportionally to the decrease of the O-2A progenitor number, and of BrdU+ cells, suggesting that HA acts (directly or indirectly) on O-2A cell proliferation. This effect, which was seen for concentrations as low as 0.1 micrograms/ml, was HA specific and was not observed with other glycosaminoglycans. When primary cultures were performed in the presence of hyaluronidase-digested or HA-depleted (by passage on a HN column) fetal calf serum, the total number of O-2A lineage cells was dramatically increased (100%, p < 10(-4)) in comparison with control cultures in standard fetal calf serum. Platelet-derived growth factor increased the total number of O-2A lineage cells and of (Galc+) oligodendrocytes. This effect was opposed by HA dose dependently. The effect of HA was significantly inhibited by HN (30%, p < 10(-4)). HN had, however, no effect when it was added to culture in the presence of hyaluronidase in fetal calf serum, suggesting its effect was only due to its binding to HA. During cell maturation, HA disappears as HN appears. This and the fact that HA and PDGF have opposite effects suggest an effect of these factors, or of their balance, on myelination.

Animals↗

PubMed1994

Cell growth suppression of astrocytoma C6 cells by glial fibrillary acidic protein cDNA transfection.

The cellular functions of the intermediate filament family including glial fibrillary acidic protein (GFAP) are not well known yet beyond their roles as structural elements of cells. Expression of GFAP, which is specific in astrocytes and regulated developmentally, suggests its involvement in cell growth and differentiation of astrocytes. We transfected murine GFAP cDNA into a rat astrocytoma C6 cell line to assess the specific effect of GFAP on cells. Two stable GFAP-transfected cell lines, GFC6-5 and GFC6-6, exhibited a series of morphological and growth characteristics that distinguish them from their counterparts, i.e., NeoC6 cells transfected only with the neomycin-resistant gene, and native C6 cells. Both GFC6-5 and GFC6-6 cells showed elongated cell shapes with extended processes rich in GFAP, markedly suppressed cell growth, and decreased bromodeoxyuridine uptake. Western blot analysis revealed a remarkable increase of GFAP expression in GFC6-5 and GFC6-6 compared with that in NeoC6 and C6, in contrast to similar vimentin expression in all cell lines. The results indicate that the expression of GFAP has dramatic effects on cell morphology and cell growth suppression in C6 cells, suggesting that GFAP may function as a tumor suppressor in astrocytoma.

Animals↗

PubMed1994

Neural cell adhesion proteins and neurological diseases.

Neural cell adhesion proteins play important roles in neural development and are involved in various neurological diseases. P0, a major protein in mammalian peripheral myelin, mediates not only homophilic cell adhesion but also neurite outgrowth. The P0 glycopeptide inhibits the cell adhesion, but not the neurite outgrowth. Several point mutations of the P0 gene in human chromosome 1q22-23 were found in Charcot-Marie-Tooth (CMT) disease type 1B and Dejerine-Sottas (DS) disease. PASII/PMP22 and connexin 32 were also reported as target proteins of similar hereditary neuropathies. L1 is a large multifunctional protein involved in cell adhesion, neurite outgrowth, fasciculation, and neuronal cell migration. A short isoform of L1 localizes in non-neuronal cells in contrast to the complete L1 exclusively expressed in neurons. Recently various L1 mutations have been reported in X-linked hydrocephalus, MASA syndrome with mental retardation and spastic paraplegia type 1. Further studies on the mutations and disease phenotypes are important and interesting.

Animals↗